From European patent document EP-PS 0 146 716 it is known how to construct the supporting structure of a vehicle body by using node connectors to join together a plurality of extruded aluminum frame sections. The node connectors are formed as cast light metal pieces. Depending upon the node connection location, the ends of the extruded aluminum sections are secured to the cast node elements by mounting on a specially molded support surface or are received within a shell enclosure and are then welded in place. For certain connecting regions, such as for example where two extruded aluminum sections are in a substantially, mutually perpendicular abutment with one other, it is advisable and more economical to make a direct connection without using the cast node connectors.
In the case of heat treatable aluminum alloys, it is well known that thermal welding produces a considerable decrease in the strength of the welded aluminum piece immediately adjacent the weld seam in the so-called "zone of thermal influence." In particular, a welded joint oriented in a transverse direction with respect to an extruded aluminum section is particularly critical since the weld weakens the extruded aluminum section in the transverse plane passing through it. Such joints may fail and be torn off at heavily loaded connection points, especially during an impact to the vehicle where extremely high load conditions are present.
It is also known from European patent document EP-PS 0 146 716 how to join the B post or B pillar directly to the sill of the vehicle where both frame elements are formed as extruded aluminum sections. A surrounding weld seam applied in the usual manner is not desirable here since this joint is particularly vulnerable to a side impact and the resulting strength reduction presents a danger that the B post will be torn off at the joint connection with the sill. Accordingly, in order to avoid weakness in the transverse direction of the B post, a surrounding transverse weld seam should be avoided. However, a weld seam joining the B post to the sill in the interior of the vehicle is essential for reasons of rigidity and for increasing fatigue strength since this area of the joint is subjected to extremely high load conditions.
German patent document DE 21 28 281 discloses a welded joint between two extruded aluminum sections which are fitted together at an angle whereby one or more substantially triangular side pieces are fitted to the corner regions formed by the two extruded aluminum sections. The triangular piece is butt-welded in place along adjacent lengthwise edges of the two extruded aluminum sections. Moreover, the outer bearing edges of the flush-mounted triangular pieces are also butt-welded to each of the two extruded aluminum sections. Such a welded joint, while adequate for support in a vertical plane, is of limited use for the extremely heavy loads associated with a side impact at the joint between the sill and the B post since it does not surround the piece in the transverse direction.
Accordingly, there is a definite need in the art for a T-shaped welded joint connection between two mutually perpendicular extruded aluminum hollow section members, such as a longitudinal sill member and an upstanding B post, which is capable of withstanding heavy side loads.